282 ROCHESTKR ACADEMY OF SCIENCE. [May 14, 



of Spain, Trinidad. A contract according to the proposed terms was 

 then made by this company with the Trinidad government for 

 twenty-one years. In 1893 the government received a revenue of 

 about $150,000 from the lake. 



In addition to the forty cents a ton for the pilch and one dollar 

 twenty cents a ton export duty, the cost of digging the pitch, carting 

 it to the pier at LaBrea and loading it on the steamer is about one 

 dollar fifty cents a ton, or in all three dollars ten cents a ton on board. 



The pitch sent to the United States is shipped in bulk as it is 

 dug out from the lake. In the hold of the vessel the pitch softens 

 with the heat and the pieces coalesce into a semi-fluid mass. On 

 reaching the north the mass becomes hard and has to be broken out 

 with picks as when first taken from the lake. In some cases, from 

 unusual heat or a long voyage, the mass became so soft as to list 

 to leeward, and the vessels being unable to right themselves have 

 been wrecked. 



The pitch sent to Europe is first refined at LaBrea. When 

 melted all foreign matter, amounting to from 10 to 20 per cent., floats 

 or settles to the bottom, and the pure asphaltum, there known as 

 "pitch epuree", is drawn off and shipped to Europe in barrels. 



Most of the Trinidad asphaltum used in this country is bought 

 crude of the Trinidad Asphalt Company by the Warren Chemical and 

 Manufacturing Company and refined at its works at Hunters Point, 

 New York, and then sold to the different paving companies. One of 

 the paving companies, the Barber, has a refinery of its own at 

 Hunters Point and another at Washington. 



AsPHALTic Pavements. 



The Trinidad Lake asphaltum in its natural condition is too 

 brittle for our northern cold. To correct this it is toughened by 

 using with it about 12 per cent, of another bitumen higher in the 

 scale, viz., the residuum of petroleum. This combination is both 

 hard and tough, hard enough not to become soft in the heat of 

 summer and tough enough not to crack in the cold of winter. In 

 this condition it is known as bituminous mastic, or paving cement. 



To this mastic or cement fine, sharp sand and powdered 

 carbonate of lime are added, in the jjroportion of 12 to 16 per cent, 

 mastic, 73 to 67 per cent, sand, and 15 to 17 per cent, carbonate of 

 lime, to make a pavement which will resist wear. 



